Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Operational use of Primary and Secondary Channel

Tech Log The very best in practical technical discussion on the web

Operational use of Primary and Secondary Channel

Old 29th May 2020, 02:12
  #1 (permalink)  
Thread Starter
Join Date: May 2020
Location: Singapore
Posts: 1
Likes: 0
Received 0 Likes on 0 Posts
Operational use of Primary and Secondary Channel

Hello, I am new to this forum, I am an engineer working for a project to support VHF comms for aircrafts. I would like to clarify the operational use of primary and secondary VHF channels. I understand that the primary channel is used for ATC, what is the usage of the secondary? Only as a backup?
Thanks to anyone willing to answer
Luca Simonini is offline  
Old 29th May 2020, 23:33
  #2 (permalink)  
Join Date: Oct 2009
Location: Australia the Awesome
Posts: 399
Received 0 Likes on 0 Posts
In my company, and most Iíve flown in, 121.5 unless operationally required to be on another frequency. This would normally only be for Parallel runway Approaches, calls to the company/ground handlers, and in Australia, we have some airports without ATC, so then we use the 2nd VHF for the local traffic frequency (CTAF).

Hope that helps
Roj approved is offline  
Old 30th May 2020, 07:41
  #3 (permalink)  

Avoid imitations
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 14,583
Received 442 Likes on 234 Posts
I use mine to tune into ATIS broadcasts or to contact a second enroute airfield where necessary. I’ve also used it to contact handling agents.

I would think most others do similar.
ShyTorque is offline  
Old 30th May 2020, 07:55
  #4 (permalink)  
Join Date: Nov 1999
Location: UK
Posts: 2,524
Received 124 Likes on 79 Posts
VHF 1 is usually used for "primary" communications with ATC. On many aircraft, the VHF 1 box is kept alive - for example by battery - when the aircraft electrical system is compromised. So it makes sense to use VHF 1 for primary ATC comms rather than having to switch boxes and frequencies in the event of electrical failure.

VHF 2 is used as a back-up for VHF 1 in the event of failure, and also for "house keeping" functions such as talking to handling agents, obtaining weather, talking to company operations, and in some cases - for example Gibralter - contacting the destination ATC to obtain approach clearance, while VHF 1 is tuned to an en-route ATC agency.

Thank you Denti, (below). I forgot to mention monitoring guard on VHF 2 Oops!

Last edited by Uplinker; 31st May 2020 at 08:49.
Uplinker is offline  
Old 30th May 2020, 18:41
  #5 (permalink)  
Join Date: Mar 2001
Location: I wouldn't know.
Posts: 4,499
Likes: 0
Received 0 Likes on 0 Posts
Pretty much the same around the industry i guess.

VHF 1 is for ATC, VHF 2 usually kept on guard listening watch, and can be used operationally for weather, ops and the like if those are not reachable via datalink. VHF 3 is on datalink and not usually used for voice comm.

Denti is offline  
Old 31st May 2020, 11:15
  #6 (permalink)  
Join Date: Jun 2001
Location: The middle
Posts: 567
Received 10 Likes on 4 Posts
Also in many parts of the world box 2 is needed for inflight broadcast procedures and negotiating entry at FIR boundaries, so ATC functions in addition to monitoring guard and house keeping stuff.
excrab is online now  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.